1. Field of the Invention
The invention relates to an image processing apparatus for high-efficiently encoding/decoding an image signal and a method for such an apparatus.
2. Related Background Art
In recent years, owing to the advancement of digital signal processing techniques, a large amount of digital information such as motion image, still image, audio sound, or the like can be high-efficiently encoded, recorded to a small magnetic medium, and transmitted to a communication medium. Multimedia equipment which can mixedly handle a motion image and a still image and, further, a plurality of video images of different resolutions by using those techniques is being examined.
FIG. 1 shows a conventional constructional example of a high efficient coding apparatus which can mixedly record/reproduce a motion image of a low resolution and a still image of a high resolution.
In FIG. 1, either a low resolution video signal or a high resolution video signal is selectively inputted to a video signal input terminal 101 and supplied to a low resolution video coding circuit 102 and a high resolution video coding circuit 103. Each of the low resolution video coding circuit 102 and high resolution video coding circuit 103 performs processes such as orthogonal transformation, quantization, and variable length coding to the signal which is supplied, thereby high-efficiently encoding the signal and transmitting the encoded signal to a switching circuit 104.
The switching circuit 104 selects the signal supplied from the low resolution video coding circuit 102 when the input signal to the input terminal 101 is the low resolution video signal. The switching circuit 104 selects the signal supplied from the high resolution video coding circuit 103 when the input signal to the input terminal 101 is the high resolution video signal. The selected signal is recorded onto a recording medium 105.
An audio signal which is inputted to an audio signal input terminal 106 is encoded by an audio coding circuit 107 and recorded onto the recording medium 105. An additional information signal which is inputted to an additional information input terminal 108 is encoded by an additional information coding circuit 109 and recorded into a video recording area on the recording medium 105.
That is, in the apparatus, only either the low resolution video coding circuit 102 or the high resolution video coding circuit 103 is validated by the switching circuit 10-4 and only either one of their outputs is recorded onto the recording medium 105, hereby realizing the high efficient coding for the video signals of a plurality of resolutions.
FIG. 2 shows a constructional example of a conventional decoding apparatus.
In FIG. 2, a video code recorded on a recording medium 201 is supplied to a low resolution video decoding circuit 202 and a high resolution video decoding circuit 203. Each of the low resolution video decoding circuit 202 and high resolution video decoding circuit 203 performs processes such as variable length decoding, inverse quantization, and inverse orthogonal transformation to the supplied video code, thereby decoding it to the original video signal and transmitting the decoded signal to a switching circuit 204.
The switching circuit 204 selects the signal supplied from the low resolution video decoding circuit 202 when the video code supplied from the recording medium 201 is the low resolution video image. The switching circuit 204 selects the signal supplied from the high resolution video decoding circuit 203 when the video code supplied from the recording medium 201 is the high resolution video image. The selected signal is outputted to a video signal output terminal 205.
An audio code recorded on the recording medium 201 is decoded to an audio signal by an audio decoding circuit 206 and outputted from an audio signal output terminal 207. Similarly, an additional information code recorded on the recording medium 201 is decoded to the additional information signal by an additional information decoding circuit 208 and outputted from an additional information signal output terminal 209.
In the above conventional apparatus, when the motion image of the low resolution and the still image of the high resolution are mixedly processed, since the different coding/decoding circuits are used for the motion image of the low resolution and the still image of the high resolution, a very large circuit scale is required. Generally, in many cases, the MPEG1 system is used for the coding/decoding circuit of the motion image of the low resolution and the JPEG system is used for the coding/decoding circuit of the still image of the high resolution. Further, the recording medium on which the still image of the high resolution has been recorded by the above apparatus cannot be used at all in a conventional apparatus corresponding only to the motion image of the low resolution.
As a simpler conventional construction, an apparatus such that a still image of a high resolution is divided into a plurality of still images of a low resolution and a coding/decoding circuit of a low resolution is used in common has been proposed. However, since distortion, aliasing, and oscillation occur in the image due to the image division, reproducibility in case of reproducing an image by the conventional apparatus is low. Particularly, when still images are continuously reproduced in a manner similar to a motion image, such distortion, aliasing noise, and oscillation occur like noises.
In consideration of the circumstances as mentioned above, it is an object of the invention to provide an image processing apparatus which can mixedly perform high efficient coding/decoding processes to a low resolution image and a high resolution image by a small circuit scale while a high picture quality is maintained without losing compatibility with an apparatus corresponding only to the low resolution image and to provide a method for such an apparatus.
For this purpose, according to one aspect of the present invention, there is provided an image processing apparatus/method comprising the steps of: selectively inputting a first image signal and a second image signal whose resolution is higher than that of the first image signal; separating a low frequency component and a high frequency component from the second image signal; encoding the first image signal or the image signal of the separated low frequency component; and encoding the image signal of the separated high frequency component.
According to another aspect of the present invention, there is provided an image processing apparatus/method comprising the steps of: separating a low frequency component and a high frequency component from a first image signal; converting a resolution of the image signal of the low frequency component and encoding the converted image signal; encoding the image signal of the high frequency component; and decoding the image signal of the low frequency component and the image signal of the high frequency component which were independently encoded, wherein the encoded image signal of the low frequency component is decoded, the encoded image signal of the high frequency component is decoded, and the decoded image signal of the low frequency component and the decoded image signal of the high frequency component are synthesized.
According to still another aspect of the present invention, there is provided an image processing apparatus/method for storing an encoded motion image signal constructed by (nxc3x97m) pixels into an image storage area on a recording medium, comprising the steps of: receiving an image signal constructed by (Nxc3x97M) pixels (N greater than n, M greater than m); extracting the image signal of (nxc3x97m) pixels corresponding to a low frequency component of the received image signal; encoding the extracted image signal of (nxc3x97m) pixels; storing the encoded image signal into the image storage area on the recording medium; extracting a high frequency component of the image signal constructed by (Nxc3x97M) pixels; encoding the extracted high frequency component; and storing the encoded high frequency component into a storage area different from the image storage area on the recording medium.
According to further another aspect of the present invention, there is provided an image processing apparatus/method comprising the steps of: inputting an image signal; extracting a low frequency component signal from the image signal; extracting a first high frequency component signal from the image signal; extracting a second high frequency component signal from the low frequency component signal; encoding the low frequency component signal; and encoding the first high frequency component signal and the second high frequency component signal.
According to further another aspect of the present invention, there is provided an image processing apparatus/method comprising the steps of: inputting encoded signals provided by separating a low frequency component and a high frequency component of an image and encoding the separated frequency components, respectively; decoding the encoded signal of the low frequency component, thereby forming a first low frequency component signal; extracting a second low frequency component signal from the first low frequency component signal; decoding the encoded signal of the high frequency component, thereby forming first and second high frequency component signals; and synthesizing the second low frequency component signal and the first and second high frequency component signals, thereby forming an image signal of a predetermined resolution.
According to further another aspect of the present invention, there is provided an image processing apparatus/method comprising the steps of: inputting first image data; dividing the first image data into first low frequency component data and first high frequency component data; encoding the first low frequency component data; encoding the first high frequency component data; extracting second high frequency component data from the first low frequency component data; and encoding the second high frequency component data in accordance with predetermined conditions.
According to further another aspect of the present invention, there is provided an image processing apparatus/method comprising the steps of: inputting encoded data provided by separating image data into first low frequency component data and first high frequency component data and encoding the separated frequency components respectively, and encoded data obtained by encoding a second high frequency component extracted from the first low frequency component data; decoding the encoded data of the first low frequency component; decoding the encoded data of the first and second high frequency components; synthesizing the decoded first low frequency component data and the decoded second high frequency component data and outputting synthetic data; and synthesizing the synthetic data and the decoded first high frequency component data.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.